Quality xerographic reproductions



Nov. 19, 1968 D. MALONE ETAL 3,411,932

QUALITY XEHOGRAPHIC REPRODUGTIONS 4 Sheets-Sheet 1 Filed Sept. 23, 1964INVENTORS DAVID L. MALONE B EDWARD F. MAYER [5% A? w M ATTORNEYS D. 1..MALONE ET AL 3,411,932

QUALITY XEROGRAPHIC REPRODUCTIONS Nov. 19, 1968 4 Sheets-Sheet 2 FiledSept. 23, 1964 INVENTORS DAVID L. MA

LONE

B EDWARD F. MAYER M M LZMVW 0 M;

ATTORNEYS Nov. 19, 1968 D. 1.. MALONE ET AL QUALITY XEROGRAPHICREPRODUCTIONS 4 Sheets-Sheet Filed Sept. 23, 1964 FIG.4

INVENTORS ER NE M w A T MF- M ow m V me NOV. 19, 1968 ET AL 3,411,932

QUALITY XEROGRAPHI C REPRODUCTIONS I 4 Sh t -Sh t 4 Filad Sept. 23, 1964I ee s ee INVENTORS DAVID L MALONE B! I jaw/x500 FZMAYER ATTORNEYSUnited States Patent 3,411,932 QUALITY XEROGRAPHIC REPRODUCTIONS DavidL. Malone, East Rochester, and Edward F.

Mayer, Pittsford, N.Y., assignors to Xerox Corlgirition, Rochester,N.Y., a corporation of New Filed Sept. 23, 1964, Ser. No. 398,690 14Claims. (Cl. 117-175) ABSTRACT OF THE DISCLOSURE Method and apparatusfor producing xerographic reproductions of graphic information on asupport, substantially free of undesirable background, fromxerographical- 1y developed images of high density deposits of powderparticles in the image areas and low density unavoidably depositedrandomly positioned powder particles in the non-image areas in which thesupport and powder deposits are exposed to a source of radiation for apredetermined time period at an intensity sufficient to fuse the highdensity powder deposits to the support but insufficient to fuse the lowdensity background deposits of powder particles to the support and theunfused low density background deposits of powder particles aresubsequently removed from the support.

This invention relates to Xerography and more particularly to novelmethod and apparatus for improving the quality of xerographicreproductions characterized by being substantially free of developerpowder deposition in unwanted, non-image areas.

In the process of xerography, for example, as disclosed in CarlsonPatent US. 2,297,691, issued Oct. 6, 1942, a xerographic platecomprising a layer of photoconductive insulating material on aconductive backing is given a uniform electric charge over its surfaceand is then exposed to the subject matter to be reproduced, usually byconventional projection techniques. This exposure discharges the plateareas in accordance with the radiation intensity that reaches them, andthereby creates an electrostatic latent image on or in thephotoconductive layer. Development of the latent image is effected withan electrostatically charged, finely-divided material such as anelectroscopic powder that is brought into surface contact with thephotoconductive layer and is held thereon electrostatically in a patterncorresponding to the electrostatic latent image. Thereafter, thedeveloped xerographic image is usually transferred to a support surfaceto which it may be fixed by any suitable means.

The xerographic process is now widely known and has achieved widecommercial success by incorporation into automatic machines able toproduce high quality reproductions at a rapid rate. These machines,producing literally millions of copies each month, utilize a xerographicplate in the form of a rotating cylindrical drum which sequentiallypasses through the various processing steps for effecting copyreproduction. With each cycle of operationthe drum is generally cleanedof residual powders following the transfer step in order to prepare thedrum for the next complete cycle of operation. These machines aresubstantially fully automatic from the time an operator places anoriginal in copying position to the emergence of the final copy whichmay optionally be one or many from a single original.

A problem which has handicapped optimum quality of these reproductionshas been the scattered deposition of unwanted xerographic developerpowder in the background or non-image areas of the reproduction. Thisdifliculty is generally attributed to the development system, but mayalso be attributed to dirty original powder contaminated optics or thelike causing the unwanted powder to ultimately appear on the finalreproduction. That is, various development systems are known in the artincluding powder cloud, brush, magnetic brush, cascade or the like eachof which are effective to present the de veloper powder termed toner tothe charge pattern to effect its development. In the cascade system, thedeveloper comprises a combination of a carrier support in the form ofcarrier beads and toner, as disclosed for example in Walkup Patent US.2,638,416 and is cascaded over the latent image on the photoconductivelayer. Whatever development system is employed, the toner is agitated onits support whereby a triboelectric charge of :a desired polarity isproduced on the toner and a charge of opposite polarity is produced onthe support from which the toner is removed. The triboelectricprocesses, however, are statistical and it has been known that not alltoner particles are charged to the same degree or to the same polarityas that sought to be obtained. As a result of this incompletetriboelectric eifect, it has been known that the incompletely chargedtoner tends to deposit spuriously in non-image areas of the xerographicplate to be later transferred to the final copy sheet and fused thereon.At the same time, it has been known that additional toner particlesdeposit in the non-image areas by purely mechanical forces when thedeveloper is presented to the photoconductive layer.

It should be appreciated, therefore, that prior to fusing, all thedeveloper, including that comprising the wanted image as well as theunwanted background, is loosely held posing a problem of diflicultselective removal. At the same time, following fusing all the powder hasheretofore been too permanently afiixed as to render the problem ofselective removal even more difficult. Efforts to remove this backgrounddeposition have therefore been unsuccessful and accordingly, the need toeffect its elimination has long been recognized.

In addition to the background problem described above, it has long beendesired to enable selective elimination of unwanted image areasreproduced onto the copy sheet as from the original, the transportmechanism or the like. As for example, business considerations such asstatements of account, frequently require the updating of informationfrom the original to the copy in order to supply the customer with themost current of information. This likewise has been a problem in that ithas not been possible to effect this elimination of unwanted image areaswithout manual intervention prior to fusing as by intercepting the copysheet and wiping away loosely held toner in the undesired areas.

Now in accordance with the instant invention, there is provided novelmethod and apparatus adapted to provide improved xerographic copy by theconsistent elimination of scattered background deposition and at thesame time possessing the ability to automatically eliminate unwantedimage areas from the final copy.

Accordingly, it is an object of the invention to provide novel methodand apparatus for effecting improved quality xerographic reproductions.

It is a further object of the invention to provide novel method andapparatus whereby improved xerographic reproductions are formed on acopy sheet substantially devoid of scattered developer powder in thebackground non-image areas.

It is a further object of the invention to provide novel method andapparatus for improving the quality of xerographic reproductions byeliminating the reproduction of unwanted image areas while alsoeliminating scattered developer toner from the background non-imageareas of the reproduction.

It is a still further object of the invention to provide novel methodand apparatus which when incorporated into an automatic Xerographicmachine effects an economical improvement for producing high qualityxerographic reproductions whereby the commercial success thereof issubstantially enhanced.

These and other objects are achieved in accordance with the invention byemploying a combination of fusing and cleaning in which the fusingmember is operatively effective selectively for fusing to the supportsheet the electroscopic toner material in mass densities correspondingto an image while at the same time is substantially ineffective forfusing scattered relatively smaller mass densities corresponding toscattered background deposition, Since fusing is selective as aforesaid,background deposition can subsequently be removed in the cleaning phaseas by wiping without deleteriously affecting the image areas of thereproduction. In addition to the inherent property of selective fusing,the fusing element employed in the invention is further characterized byhaving substantially zero warm-up time as compared to approximately 20seconds to 15 minutes for prior units for which continuous operation isrequired and substantially zero residual heat which enablessubstantially immediate discontinuance of the fusing operation. Thislatter feature permits de-energizing the unit in timed relation to thepassing of reproduced unwanted image areas as to effect theirelimination in the subsequent cleaning step.

Further objects and features of the invention will become apparent whilereading the following description in connection with the followingdrawings wherein:

FIG. 1 is a schematic sectional elevation of an automatic apparatuswhich includes fusing and cleaning the final reproduction in accordancewith the invention:

FIG. 2 is an isometric view of the fuser illustrated schematically inFIG. 1;

FIG. 3 is an isometric view of the cleaner assembly illustratedschematically in FIG. 1;

FIG. 4 is an isometric view of a hand process step for cleaning thefinal reproduction following fusing alternative to the cleaningapparatus in FIG. 1;

FIGS. 5 and 6 are alternative forms of apparatus as may be utilized forcleaning the reproduction following fusing in accordance with theinvention; and,

FIG. 7 is a fragmentary isometric view of apparatus illustrating atemporary de-energizing of the fuser permitting unwanted image areas onthe reproduction sheet to pass the fuser unfused.

For a general understanding of the Xerographic processing system inwhich the invention is incorporated, reference is made to FIG. 1 inwhich the various system components are schematically illustrated. TheXerographic apparatus described herein may be an adaptation of the typedisclosed in Eichler et al. Patent US. 2,945,434. As in all Xerographicsystems based on the concept disclosed in the above cited Carlsonpatent, a radiation image of copy to be reproduced is projected onto thesensitized surface of a Xerographic plate forming an electrostaticlatent image thereon, Thereafter, the latent image is usually developedwith an electorscopically charged developing material to form aXerographic powder image, corresponding to the latent image on the platesurface. The developed image is then transferred to a support surface towhich the image is permanently affixed by means of a fuser apparatus- Asshown in FIG. 1 there is illustrated a light-tight cabinet 10 forenclosure and containment of all the operative components. Copy to bereproduced, such as a book, sheet or the like, here designated 11, issupported at a copy station 12. The copy station includes a horizontallyarranged transparent platen support 13, such as glass, on which the copyrests in position to be optically scanned. Projection of the copy imageis achieved by means of a scanning mechanism that includes a pair oftransversely extending fluorescent lights 22 and 23 that are adapted tomove horizontally from the position shown solid to the position showndashed as more fully described in the above-cited Eichler patent. Lightshields 24 and 25 prevent stray light from being transmitted from thelamps other than that which is utilized for illuminating the copy above.An image of the illuminated copy is reflected through objective lens 26,which moves horizontally in conjunction with the lamp, for projecting animage downwardly through an aperture slit 28 and onto the surface of aXerographic plate in the form of rotating drum 29.

Xerographic drum 29 includes a cylindrical member mounted in suitablehearings in the frame of the machine and is driven in a counterclockwisedirection by a motor 30 at a constant rate that is proportional to thescanning rate of the copy, whereby the peripheral rate of the drumsurface is identical to the scan rate of the reflected light image. Thedrum surface comprises a layer of photoconductive insulating material31, which may for example, be vitreous selenium, supported on aconductive backing 32, such as aluminum. Prior to exposure, the drum surface is sensitized by means of a corona generating device 33, which maybe an adaptation of the type disclosed in Vyverberg Patent US. 2,965,756and which is energized from a suitable high potential source (notshown).

The exposure of the drum to the light image discharges thephotoconductive layer in the areas struck by light, whereby thereremains on the drum a latent electrostatic image in image configurationcorresponding to the light image projected from the copy. As the drumsurface continues its movement the electrostatic latent image passesthrough a developing station 40 in which a twocomponent developingmaterial 41, which may be the type disclosed in Walkup patent supra iscascaded over the drum surface by means of a developing apparatus 42.

In the developing apparatus, the two-component developing material 41 iscarried upwardly by conveyor 43 driven by suitable drive means andreleased onto chute 44 wherefrom it cascades down over the drum surfaceeffecting development of the latent image thereon. Toner component 45 ofthe developer that is consumed in developing is stored in dispenser 46and is released in amounts as controlled by the dispensing mechanism.

After developing, the powder image passes through an image transferstation 50 at which the powder image is transferred by means of a secondcorona generating device 52, similar to corona generating device 33mentioned above, to a sheet of copy paper 53. The copy sheets arearranged in stack form on a supply tray 54 and are fed therefromindividually by means of a mechanical feeder 55 adapted to feed the topsheet of the stack through driven feed rollers 56 which direct the sheetmaterial into contact with the rotating drum in coordinated registrationwith the arrival of the developed image at the transfer station.

Following transfer, a pick-off mechanism 57 ensures removal of the copysheet from the drum surface wherefrom the copy sheet is directed onto anendless conveyor 58 whereby the copy sheet is carried past the fusingand cleaning devices of the invention respectively and designated as 60and 61. As will be more fully described below, the image is permanentlyaflixed thereat by the fuser onto the copy sheet while unwantedscattered powder deposition in the background areas is removed by thecleaning device. Thereafter, the finished copy passes through furtherfeed rolls into a vertical conveying system by means of which the copyis delivered to a copyholder 66 supported along the top portion ofcabinet 10 from where it may conveniently be removed by an operator.

After transfer, the Xerographic drum surface passes through a cleaningstation 70 at which the surface is brushed by cleaning brush assembly71, whereby residual developing material remaining on the drum surfaceis removed. The powder removed from the drum surface is exhaustedthrough port 72 by means of a suction provided from fan 73 and becomeslodged in a removable filter bag 74. The drum surface then passesthrough a discharge station 75 at which it is illuminated by afluorescent lamp 76 whereby the drum surface in this region iscompletely flooded with light to remove any electrostatic charge thatmay remain thereon. Suitable light traps are provided in the system toprevent any light rays from reaching the drum surface other than theprojected image, during the period of drum travel immediately prior tosensitization by corona generating device 33 until after the drumsurface is completely passed through the developing station 40.

Refer now also to FIG. 2 in which the fusing apparatus of FIG. 1 is morecompletely illustrated. As there shown, the fuser includes twosemi-annular machined rings 80 and 81 adapted for mounting within theapparatus of FIG. 1 Each of the rings are pierced to receive an interiorpolished reflector housing 82 which is semicircular, terminating alongits lower portion in a pair of oppositely arranged flange members 83 and84 extending toward each other obliquely to the horizontal and forming acontinuous exposure slit 85 therebetween. Axially supported in thehousing and extending aligned parallel above slot 85 is a tubular typeenveloped lamp 86 connected to a terminal block 87 to which is connectedan adjustable transformer 88. The lamp is characterized by thecapability of emitting a predominance of near infrared radiation of wavelength generally shorter than 2 /2 microns and corresponding to afilament temperature of approximately 2500" K. With the arrangementshown, the lamp is positioned such that the polished inner surface ofthe housing 82 reflects an image of the lamp filament onto a copy sheet89 passing therebelow to fuse images 90 without significantly affectingloosely scattered toner particles 91 on or about the background areas.Other reflector configurations such as elliptical, double parabolic,etc. can likewise be used to image the filament of the fuser source ontothe copy sheet.

The exact conditions under which the lamp is operated is controlled bythe voltage supplied by means of variable transformer 88 in order tomaintain the desired filament temperature. It has been found that paperconventionally employed for xerography is highly reflective in the namedwavelength range such that the lamp when adjusted to optimum settingsemits energy that is selectively effective in only heating the largedensity mass of developer toner particles representing the image. Thiscan be explained on the theory that the portion of radiant energy, suchas near infrared radiation directed against the toner images is absorbedand the images become heated. At the same time the support surface beinghighly reflective to the wave length of emission, reflects rather thanabsorbs, the received radiation. Accordingly, the radiant energystriking the usually glazed paper surface, lighter in color than thedeveloper, is not converted into heat energy while the developers beingpigmented, generally black, are high- 1y heat absorbent to convert theradiation into heat energy to become fused to the paper surface. At thesame time, the scattered toner in and about the background areas havesuch insignificant mass density that they absorb insuflicient quantitiesof radiation to effect their fusing and the area responds reflectivelyas if in their absence. Typically, image reproductions oftypewrittencopy have image densities greater than 0.6 while most of thescattered background toner have densities of less than 0.1.

More specifically with the lamp at the desired filament temperature,approximately 75% of the energy emitted by the source lies below 2 /2microns. At this range of wave length, the paper is highly reflectivewhile the developer toner absorbs the predominance of incident energy.In the areas of image size toner deposits fusing results since theradiant energy is absorbed raising the toner temperature which in turnheats the paper by conduction. At the same time, smaller particles,representative of spurious background deposits having highersurfaceto-volume ratios, are removable since they lose much of theirabsorbed energy through reradiation and convection and heat the paperinsufliciently to effect bonding. The incident energy by which fusing isaccomplished consists generally of direct radiation from the lamp asdefined by exit slot 85, as well as the focused radiation emittedtherethrough comprising the image of the lamp source formed by thehousing reflector system. The efficiency of the selective fusing can bemodified by the relationship between the direct radiation and the energydensity emitted by the focused radiation.

To effect fusing selectively in accordance with the invention a 1350watt lamp, marketed commercially by the General Electric Company as atype T2 /2 tungsten lamp with quartz envelope, was employed. Paperspeeds of about 1.4 inches per second produced the necessary fusing witha transformer setting corresponding to approximately 700 wattsdissipated by the lamp. Paper speeds of about 0.8 to 1.7 inches persecond were likewise suitable at this transformer setting. Since it isdesired to limit the longer Wave lengths emitted from the lamp, a blower92 operated by motor 93 is used to force large volumes of ambient air inexcess of 10 cubic feet per minute into the housing past the lampemerging through slot 85. This maintains the lamp envelope temperaturelow so that very little energy is radiated by the envelope to preventits becoming a secondary emitter which would otherwise itself partiallyeffect fusing.

Accordingly, after passing the fuser, the image areas on sheet 89 arepermanently affixed thereto while the background scattered particles areloosely retained thereon as to be capable of being wiped off orotherwise removed. Several methods have been found convenient foreffecting this removal. A first method is incorporated in an apparatusshown in FIGS. 1 and 3 for removing the background depositionautomatically. The unit 61 therefore effects cascade cleaning of thecopy sheet which is directed toward the unit through a guide slotdefined between parallel guide members 95 and 96. The sheet is thengripped by the bite of a pair of driven pinch rollers 97 and 98 whichforce the sheet into an entrance slot 118 defined in the forward part ofthe unit.

The cleaning unit 61 comprises a moderately deep disk tank 101 generallysemi-cylindrical along its bottom surface and enclosed at its ends byend walls 102 and 103 for containing a predetermined quantity ofelectroscopic carrier beads 115 adapted to attract and remove unfusedtoner from the copy sheet. The electroscopic carrier beads 115 are of atype normally employed in combination with developer toner, as describedfor example, in the Walkup patent supra, but which is employed hereininitially tonerfree. Secured to the end walls are journal plates 99between which is journaled shaft 104 having mounted thereon a paddlewheel 105 adapted to convey the carrier beads into a cascading relationwith the image side of the moving copy sheet. The paddle wheel is formedof blades 106 secured about shaft 104 and curved generally forwardly inthe direction of rotation whereby to convey the carrier beads about thetank and centrifugally release them moving relatively against thesurface of the copy sheet. Rotation of the paddle wheel is effected froma motor 110 connected via a pulley 111 and timing belt 112 to a sheave113 secured on shaft 104. The paddle wheel is rotated at a rapid rate onthe order of approximately 200 r.p.m.

A cover 116 fits over the top of tank to generally prevent the escape ofthe moving carrier and includes a plurality of vent holes 117 by whichambient pressures are maintained within.the tank. Cover 116 isphysically dimensioned less than the full width dimension of the tankand is situated as shown in the drawings to define an entrance slot 118whereby copy sheet 89 enters the tank and an exit 119 whereby the copysheet emerges therefrom. The carrier particles contained in the tankpass over the moving copy with a cascading action and by virtue of theinherent triboelectric properties generated in its continuous movement,attracts all loosely held powder from the copy sheet 89 passingthereunder. As a result, the copy sheet emerges through exit 119substantially free of all toner particles except in those image areas inwhich the powder has been previously affixed thereto. A flexible feltwiper 122, attached to the exit portion of the cover, effects a wipingaction against the passing copy to prevent the escape of carrierparticles which attach themselves to the copy surface. After repeateduse, the carrier beads become contaminated with toner and are replacedwith a fresh quantity. The emerging copy is engaged by the bite of apair of driven feed rolls 123 and 124 which force the copy through aguide slot formed by guide members 125 and 126 after which the copycontinues its movement into conveyor 65 described above.

Automatic cleaning units other than that illustrated in FIG. 1 can besubstituted therefor. Referring first to FIG. 5, there is illustrated abrush cleaning unit designated 135 past which the copy sheet 89 is fedby means of two pair of driven feed rolls 136 and 137, to pass over astationary platen 140. The cleaning unit includes one or more rotatingbrushes 138 which are driven by a motor 139 whereby the brush bristlesare rotated continuously in contact with the image surface of the copymoving therepast. The brushes are contained in a generally enclosedhousing unit 141 that is continuously evacuated by a blower unit 142operative by motor 143. The brushes, rotating continuously in contactwith the surface of the copy sheet, obtain a cleaning effect analogousto that obtained with the cascade unit described above. Preferably, thebristles are characterized as to triboelectrically attract the loosepowder particles and may, for example, comprise natural or syntheticfibers as are known in the art. The vacuum generated by means of blower142 withdraws the removed toner powder from the brush bristles fordischarge to a suitable filter means as to maintain the brush relativelyclean for long periods of time.

Still another unit for effecting cleaning is illustrated in FIG. 6 anddesignated 150. This latter unit comprises an automatic continuous feedof a soft disposable type cloth, such as cotton, in the form of acontinuous web 151. The web is supplied from a supply roll 152 wherefromit passes over a pair of soft resilient guide rolls 153 and 154 thaturge the web against the surface of the moving copy sheet and thenpasses onto a takeup roll 155 being driven by motor 156. The web movesat a relatively slow rate, as compared to the movement of copy, andpreferably travels in a direction counter to that of the copy such thatthe cleanest portion of the web encounters the lowest concentration ofscattered toner 91. With a disposable web material, the soiled consumedmaterial on the take-up roll can be discarded or cleaned for subsequentreuse.

As an alternative to cleaning the copy sheet within the apparatus in themanner described above, it can instead be permitted to emerge therefromwith the scattered background toner 91 still contained thereon. As shownin FIG. 4, the background deposition can be removed by means of a softcotton or the like 130 which is hand-wiped across the copy surface. Itis to be noted in the figure that the top portion of the copy sheet overwhich the cotton has passed is substantially or entirely free ofscattered background deposition 91 while that in the lower portion yetto be wiped still contains these particles.

As previously described above, a selected lamp 86 is preferablycharacterized in its ability to achieve radiant fusing operatingconditions substantially instantaneously when energized. At the sametime, it has extremely low heat residual as to discontinue significantemission of fusing energy within approximately 100 milliseconds afterbeing de-energized. This inherent property of the preferred lampstructure enables controlled energizing and de-energizing in a mannerwhereby selected linearly lateral portions of the copy sheet are able tomove past the fuser without fusing relatively dense image masses oftoner material which otherwise would be fused. Particularly, as statedabove, it has long been desired to eliminate unwanted image areas forupdating information as described above. Various cams, gears, timers orthe like can be suitably adapted for switching the fusing circuit intimed relation to the movement of the copy sheet past the fusermechanism. As shown in FIG. 7 there is illustrated a paper transport 161which may be of a type described in Eichorn et al. Patent 3,099,943. Thetransport employs a gripper bar 162 connected to a pair of oppositelyarranged endless driven chains 164 having a plurality of individualpaper grippers 163 for advancing copy sheet 89 past the fusing unit.

In order, by way of example, to de-energize the fusing lamp at theappropriate transport position of sheet travel as to prevent fusingalong the leading edge of copy, there is provided a microswitch 165supported adjacent to one of the chains intermediate the chain and theside edge of the copy sheet. The microswitch is connected in the fusercircuit and has a long contact arm 166 extending vertically inclinedfrom the switch in the path of the moving gripper bar for engagementthereby. When engaged by the gripper bar the switch de-energizes thefuser for a controlled time period until the gripper bar has completelytraversed the contact arm 166. The length of contact is commensuratewith the dimension of the copy material to be deleted such that with thecopy sheet traveling at 1.4 inches per second, the fuser is de-energizedfor a period of approximately 0.35 second coincident with the time atwhich the portion to be deleted arrives and passes the fusing position.Subsequent cleaning of the copy sheet as described above effects removalof the unfused deletable portion. Obviously suitable time delays can beprovided to adapt the controlled de-energizing of the fuser to anydesired portion of the copy sheet.

By the above description, there is disclosed novel method and apparatuswhereby the finished quality of xerographic reproduction is improved inthe elimination of unwanted scattered toner in the background areas. Atthe same time, there is disclosed novel method and apparatus wherebylaterally arranged deletable unwanted image portions of the reproductionformed on the copy sheet can be eliminated. The methods and apparatusdescribed form a highly expedient method of improving the overallquality without expensive or elaborate apparatus or controls as havebeen attempted heretofore. Thus, in accordance with the invention, asimple, yet highly effective means has been disclosed in resolving adifliculty that has long awaited a solution.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the drawings shall be interpreted as illustrative and notin a limiting sense.

What is claimed is:

1. A method of producing a xerographic reproduction of graphicinformation on a support, substantially free of undesirable background,from a xerographically developed image of high density deposits ofpowder particles in the image areas and low density unavoidablydeposited randomly positioned powder particles in the non-image areascomprising,

exposing said support and powder deposits to a source of radiation for apredetermined time period at an iiltensity sufficient to fuse said highdensity powder deposits to said support but insuflicient to fuse saidlow density background deposits of powder particles to said support, and

removing the unfused low density background deposits of powder particlesfrom the support.

2. A method of producing a xerographic reproduction of graphicinformation on a support, substantially free of undesirable background,from a xerographically developed image of high density deposits ofpowder particles in the image areas and low density unavoidablydeposited randomly positioned powder particles in the non-image areascomprising,

exposing said support and powder deposits to a source of radiation overa predetermined time period at a controlled intensity which producesheating of said high density powder deposits to a temperature sufficientto effect fusion to said support and which produces heating of said lowdensity powder deposits to a temperature insufiicient to effect fusionto said support, and

cleaning the image surface of said support to selectively remove theunfused low density powder deposits therefrom. 3. The method accordingto claim 2 in which the predominance of radiation emitted by said sourceis in the wavelength range of not greater than 2.5 microns.

4. The method according to claim 2 in which said cleaning step comprisescascading a quantity of electroscopic carrier particles over the imagesurface of said support to electrostatically remove loosely retaineddeveloper powder particles therefrom.

5. The method according to claim 2 in which said cleaning step compriseswiping the image surface of said support with a generally soft fibrousmaterial.

6. The method according to claim 2 in which said cleaning step comprisesbrushing the image surface of said support with a brush having bristlesrelatively free of developer powder particles thereon.

7. Apparatus for producing a xerographic reproduction of graphicinformation on a support, substantially free of undesirable background,from a Xerographically developed image of high density deposits ofpowder particles in the image areas and low density unavoidablydeposited randomly positioned powder particles in the non-image areascomprising,

a source of radiation, means for subjecting said support and powderdeposits thereon to exposure by said source of radiation for apredetermined time period at an intensity sufficient to fuse said highdensity powder deposits to said support but insufiicient to fuse saidlow density background deposits of powder particles to said support,

means for removing the unfused low density background deposits of powderparticles from the support, and

means for removing said support from exposure by said radiation sourceand for subjecting the image bearing surface thereof into operativerelationship with said powder removing means.

8. Apparatus according to claim 7, said radiation source comprising alamp which when energized emits a predominance of radiation in thewavelength range of not greater than 2.5 microns.

9. Apparatus according to claim 8, further including a housing forsupporting said lamp, said housing including a wall portion having aslot defined therein to permit emission of radiation on exposed portionsof said support.

10. Apparatus according to claim 9, said lamp housing including aradiation reflective surface positioned about said lamp to reflectivelyfocus radiation toward said slot.

11. Apparatus according to claim 7, said powder removing meanscomprising,

bearing surface of said support, and

rotatable brush means positioned to contact the image means forcontinuously rotating said brush means about the axis thereof.

12. Apparatus according to claim 7, said powder removing meanscomprising,

a continuous web of soft absorbent material positioned to contact theimage bearing surface of said support, and

means for continuously advancing said web across the surface of saidsupport.

13. Apparatus according to claim 7, said powder removing meanscomprising,

a receptacle containing a quantity of electroscopic carrier particles,

means defining a path of travel within said receptacle along which saidsupport is advanced, and

means for agitating said carrier particles within said receptacle tocontact the image bearing surface of said support to remove unfusedpowder particles therefrom.

14. Apparatus for producing a Xerographic reproduction of graphicinformation on a support, substantially free of undesirable background,from a Xerographically developed image of high density deposits ofpowder particels in the image areas and low density unavoidablydeposited randomly positioned powder particles in the nonimage areascomprising,

a source of radiant energy,

means for energizing said source of radiant energy to emit radiations ata predetermined energy level,

means for subjecting said support and powder deposits thereon toradiations emitted by said source for a predetermined time period,

said predetermined energy level and said predetermined time period beingof respective intensity and duration magnitudes to produce heating ofsaid high density deposits of powder particles in the image areas to atemperature sufficient to fuse to said support and to produce heating ofsaid low density deposits of powder particles in the non-image areas toa temperature insuflicient to fuse to said support,

cleaning means for removing the unfused low density powder particlesfrom said support without substantially affecting the fused high densitypowder deposits thereon, and

means for withdrawing said support from an operative relationship withsaid source of radiant energy and for subjecting the image bearingsurface thereof into operative relationship with said cleaning means.

References Cited UNITED STATES PATENTS 2,484,782 10/ 1949 Copley 961 X2,752,271 6/1956 Walkup et a1. 117-19 2,937,390 5/1960 Bolton et a111717.5 X 3,021,817 '2/1962 Limberger 11717.5 X 3,053,962 9/1962Cerasani et a1. 11717.5 X 3,059,614 10/1962 Limberger 11717.5 X3,060,024 10/1962 Burg t al 9628 3,081,699 3/1963 Gulko 117--1.7 X3,088,386 5/1963 Sugarman 11717.5 X 3,117,030 1/1964 Jons et al 117-17.5X 3,190,198 6/1965 Eichorn 118637 X 3,234,018 \2/ 1966 Wendt 117-175 X3,256,811 6/1966 Bach 11717.5 X

WILLIAM D. MARTIN, Primary Examiner.

E. J. CABIC, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,411,932 November 19, 1968 David L. Malone et al.

It is certified that error appears in the above identified patent andthat said Letters Patent are herebycorrected as shown below:

Column 5, line 18, "FIG. 1" should read FIG. 1. Column 9, line 62,beginning with "11. Apparatus" cancel all to and including "thereof. inline 67, sane column 9, and insert 11. Apparatus according to claim 7,said powder removing means comprising,

rotatable brush means positioned to contact the image bearing surface ofsaid support, and

means for continuously rotating said brush means about the axis thereof.Column 10, lines 21 and 22, "particels" should read particles Signed andsealed this 10th day of March 1970. (SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

